The recommendation is strong because of large effect size on patient-important outcomes related to incontinence, and because diet and exercise have many other beneficial health outcomes, have low costs, and rarely have any harms.
A systematic review «Yazdany T, Jakus-Waldman S, Jeppson PC et al. American Urogynecologic Society Systematic Review: The Impact of Weight Loss Intervention on Lower Urinary Tract Symptoms and Urinary Incontinence in Over»4 identified 39 studies, including data from 5 RCTs. Behavioral weight loss (BWL, such as diet and exercise) decreased the prevalence of stress urinary incontinence (SUI) 15% to 18% and overall urinary incontinence (UI) by 12% to 17% at 1 to 2.9 years. The certainty of the evidence was moderate to low regarding the benefit of BWL on urgency UI and overactive bladder symptoms.
A randomised controlled trial «Subak LL, Whitcomb E, Shen H et al. Weight loss: a novel and effective treatment for urinary incontinence. J Urol 2005;174(1):190-5. »1 involved 48 overweight and obese women experiencing at least 4 urinary-incontinence (UI) episodes per week. Women were randomly assigned to a 3-month liquid diet weight reduction program or a wait-list delayed intervention group. Median (with 25% to 75% interquartile range [IQR]) baseline weight was 97 kg (IQR 87 to 106) and UI episodes were 21 weekly (IQR 11 to 33). Weight reduction was 16 kg (IQR 9 to 20) in the intervention group compared with 0 kg (IQR -2 to 2) in the control group (p <0.0001). The intervention group experienced a 60% reduction (IQR 30% to 89%) in weekly UI episodes compared with 15% (IQR -9% to 25%) in the control group (p <0.0005) and had greater improvement in quality of life scores. Stress (p =0.003) and urge (p =0.03) incontinent episodes decreased in the intervention vs control group. Following the weight reduction program the wait-list control group experienced a similar median reduction in weekly UI episodes (71%). Among all women mean weekly UI episodes decreased 54% (95% CI 40% to 69%) after weight reduction and the improvement was maintained for 6 months.
Another RCT «Subak LL, Wing R, West DS et al. Weight loss to treat urinary incontinence in overweight and obese women. N Engl J Med 2009;360(5):481-90. »2 involved 338 overweight and obese women with at least 10 UI episodes per week. Women were randomly assigned to an intensive 6-month weight-loss program that included diet, exercise, and behavior modification (226 patients) or to a structured education program (112 patients).The intervention group had a mean weight loss of 8.0% (7.8 kg), as compared with 1.6% (1.5 kg) in the control group (P<0.001). After 6 months, the self-reported mean weekly number of UI episodes decreased by 47% in the intervention group, as compared with 28% in the control group (P=0.01). As compared with the control group, the intervention group had a greater decrease in the frequency of stress-incontinence episodes (P=0.02), but not of urge-incontinence episodes (P=0.14). A higher proportion of the intervention group than of the control group had a clinically relevant reduction of 70% or more in the frequency of all UI episodes (P<0.001), stress-incontinence episodes (P=0.009), and urge-incontinence episodes (P=0.04).
The same group of overweight and obese women (n=338) were combined in another study «Wing RR, Creasman JM, West DS et al. Improving urinary incontinence in overweight and obese women through modest weight loss. Obstet Gynecol 2010;116(2 Pt 1):284-92. »3 to examine the effects of the magnitude of weight loss on changes in UI assessed by 7-day voiding diary, pad test, and self-reported satisfaction with change in UI. Compared with participants who gained weight (reference), those who lost 5–10% or 10% or more of their body weight had significantly greater percent reductions in UI episodes and were more likely to achieve at least a 70% reduction in the frequency of total and urge urinary incontinence episodes at 6, 12, and 18 months.
In a bariatric surgery study «King WC, Hinerman AS, Subak LL. Seven-Year Durability of Improvements in Urinary Incontinence After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy. JAMA Netw Open 2022;5(12):e2246057. »5 1200 adults were followed for 7 years for UI. For women (n=986, median age 46 years), despite an increase in frequency and prevalence from 3 to 7 years after surgery, estimates were lower at 7 years vs preoperatively (eg, UI prevalence was 52% [95% CI 48%– 54%] preoperatively, 20% [95% CI 18%–24%] at year 3, and 30% [95% CI 26%–33%] at year 7). Time trends were similar for stress UI and urge UI.